<template>
  <div class="spec-preview">
    <img :src="defaultImg.imgUrl" />
    <div class="event" @mousemove="move"></div>
    <div class="big">
      <!-- <img :src="skuImageList[0]?.imgUrl" /> -->
      <img :src="defaultImg.imgUrl" ref="bigImg"/>
    </div>
    <div class="mask" ref="mask"></div>
  </div>
</template>

<script>
export default {
  name: "Zoom",
  data() {
    return {
      defaultIndex: 0, //默认下标
    };
  },
  props: ["skuImageList"],
  computed: {
    defaultImg() {
      return this.skuImageList[this.defaultIndex] || {};
    },
  },
  mounted() {
    this.$bus.$on("changeIndex", (index) => {
      this.defaultIndex = index;
    });
  },
  methods:{
    move(e){
      // 获取蒙版获取大图
      let mask = this.$refs.mask
      let bigImg = this.$refs.bigImg
      // 获取鼠标位置
      let mouseX = e.offsetX
      let mouseY = e.offsetY
      // 计算移动距离  鼠标位置 - 蒙版宽度的一半
      let moveX = mouseX - mask.offsetWidth/2
      let moveY =  mouseY - mask.offsetHeight/2
      // 水平边界值判断
      if(moveX<0){ //左侧
        moveX = 0
      }else if(moveX > e.target.offsetWidth - mask.offsetWidth){ //右侧
        moveX = e.target.offsetWidth - mask.offsetWidth
      }
      // 垂直边界值判断
      if(moveY<0){ //上侧
        moveY = 0
      }else if(moveY > e.target.offsetHeight - mask.offsetHeight){ //下侧
        moveY = e.target.offsetHeight - mask.offsetHeight
      }
      // 赋值给mask
      mask.style.left = moveX +'px'
      mask.style.top = moveY + 'px'
      // 不光蒙版要动 大图也得动
      bigImg.style.left = -2 * moveX +'px'
      bigImg.style.top = -2 * moveY +'px'

    }
  }
};
</script>

<style lang="less">
.spec-preview {
  position: relative;
  width: 400px;
  height: 400px;
  border: 1px solid #ccc;

  img {
    width: 100%;
    height: 100%;
  }

  .event {
    width: 100%;
    height: 100%;
    position: absolute;
    top: 0;
    left: 0;
    z-index: 998;
  }

  .mask {
    width: 50%;
    height: 50%;
    background-color: rgba(0, 255, 0, 0.3);
    position: absolute;
    left: 0;
    top: 0;
    display: none;
  }

  .big {
    width: 100%;
    height: 100%;
    position: absolute;
    top: -1px;
    left: 100%;
    border: 1px solid #aaa;
    overflow: hidden;
    z-index: 998;
    display: none;
    background: white;

    img {
      width: 200%;
      max-width: 200%;
      height: 200%;
      position: absolute;
      left: 0;
      top: 0;
    }
  }

  .event:hover ~ .mask,
  .event:hover ~ .big {
    display: block;
  }
}
</style>
